1. Field of the Invention
The present invention relates to data recording apparatuses for digitally recording data containing information representing a copyrighted work on a recording medium, such as a video tape, hard disk, or an optical disk. More specifically, the present invention relates to a video signal recording apparatus for digitally recording video signals containing information representing a copyrighted work.
2. Description of the Related Art
In recent years, video recording apparatuses which can perform digital recording of video signals on a recording medium, such as a digital video tape, a hard disk, or DVD, have rapidly become widespread, instead of those which can perform conventional analog recording on a recording medium, such as a VHS tape. When the video signals to be recorded are analog, the MPEG-2 picture compression scheme is used to first convert these analog video signals to digital video signals with a reduced amount of information and then record such digital signals on a recording medium. When the video signals to be recorded are digital, these digital video signals are recorded as they are on a recording medium.
In conventional analog recording, copying of video signals from one recording medium to another, that is, dubbing, causes significant degradation in image quality, leading to a protection of a copyrighted work included in data to be recorded. In digital recording, on the other hand, when the data to be recorded is digital, dubbing does not cause degradation in image quality as long as the there is no problem with the medium or the recording apparatus. The same goes for analog data once converted to digital data. Therefore, video signal recording apparatuses for digital recording should adopt a copyright protection technology for prohibiting illegal copying of data containing information representing a copyrighted work.
A typical copyright protection technology is described below. Signals for copyguard protection, which are superimposed on analog video signals of the National Television System Committee (NTSC) scheme for controlling dubbing, are broadly classified into Macrovision signals and Vertical Blanking ID (VB-ID) signals. A Macrovision signal is composed of an AGC pulse for inserting a pseudo-synchronizing signal and a color stripe for inverting the phase of a burst signal of a specific line. That is, an erroneous signal is inserted in a blanking period of the video signal to cause erroneous synchronization in the recording apparatus and an erroneous operation of the AGC, thereby preventing normal recording. In other words, copyright protection is achieved by a significant degradation in signal quality after copying.
A VB-ID signal, on the other hand, is composed of information of 20 bits, being inserted in the twentieth line in a vertical blanking period of an NTSC signal. The VB-ID signal includes a Copy Generation Management System-Analog (CGMS-A) signal, which represents generation management information about the work. The CGMS-A signal is composed of two bits for representing three types of information: No copying is permitted, one generation of copies may be made, and copying is permitted without restriction. Based on these three types of information, the recording apparatus determines whether a recording operation is permitted. That is, copyright protection is achieved not by degrading signal quality after copying but by restricting the number of times of copying.
The above-described Macrovision signal and VB-ID signal are signals for directly or indirectly controlling the input signal copying operation of the recoding apparatus. Also, these signals identify the input signal as containing information representing a copyrighted work. In other words, the Macrovision signal and VB-ID signal are copyguard signals which indicate that information representing a copyrighted work is mixed in the input signal and also indicate copyright information representing the degree of copyright protection for the work. A minimum period in which such a copyguard signal is inserted is one field.
With reference to FIGS. 15 and 16, a conventional video signal recording apparatus which supports Macrovision signals or VB-ID signals (CGMS-A signals) is described below. As illustrated in FIG. 15, a video signal recording apparatus DRc1 includes an input signal processing unit 101, a copyright information detecting unit 102, a recording processing unit 106, a recording unit 107, and a recording control unit 111. In the video signal recording apparatus DRc1, the input signal processing unit 101 performs a process, such as separation of a synchronizing signal or analog-digital conversion, on an analog video signal Sva to generate a digital video signal Svd for output to the recording processing unit 106. Also, the signal input unit 101 outputs the analog video signal Sva to the copyright information detecting unit 102.
The copyright information detecting unit 102 detects a Macrovision signal or a CGMS-A signal superimposed on the analog video signal Sva to extract copyright information, thereby generating a copyright information signal Scr. Based on the copyright information signal Scr, the recording control unit 111 generates a recording control signal Sc for controlling the recording operation of the recording processing unit 106.
The recording processing unit 106 performs a recording process, which complies with the recording unit 107, on the digital video signal Svd output from the input signal processing unit 101. The recording processing unit 106 preferably includes an MPEG2 image compressing means for compressing the digital video signal Svd, converting the compressed signal to a signal format for recording on a hard disk, and then outputting an MPEG image signal Smpg. The recording operation of the recording processing unit 106 is controlled by the recording control signal Sc supplied by the recording control unit 111. The recording unit 107 records the MPEG image signal Smpg supplied by the recording processing unit 106 on a digital recording medium, such as a hard disk.
A copying control operation of the video signal recording apparatus DRc1 is described below in a case where a copy guard signal, such as a Macrovision signal or a CGMS-A signals, is detected in the input analog video signal Sva. For example, when the copyright information detecting unit 102 detects in the analog video signal Sva an AGC pulse of a Macrovision signal or both of an AGC pulse and a color stripe thereof, this means that copying is prohibited. Therefore, the copyright information detecting unit 102 outputs to the recording control unit 111 a copyright information signal Scr representing that copying of the analog video signal Sva is prohibited. Since the minimum period in which a copyguard signal is inserted in the analog video signal Sva is one field, the copyright information signal Scr indicates whether copying of at least one field is prohibited.
Based on the copyright information signal Scr indicative of copying prohibition, the recording control unit 111 outputs a recording control signal Sc indicative of recording prohibition so as to stop or prevent the recording processing operation of the recording processing unit 106. When the recording processing unit 106 has been set to perform a timer-controlled recording operation, this timer-controlled recording operation is cancelled so as to be prohibited.
Next, a copying control operation of the video signal recording apparatus DRc1 is described below in a case where a CGMS-A signal is detected. When the CGMS-A signal indicates that copying is prohibited, the copyright information detecting unit 102 outputs a copyright information signal Scr indicating that copying is prohibited. The recording control unit 111 outputs a recording control signal Sc for prohibiting a recording process so as to stop or prohibit the recording processing operation of the recording processing unit 106. When the CGMS-A signal indicates that copying is permitted without restriction or that one generation of copies may be made, the copyright information detecting unit 102 outputs a copyright information signal Scr indicating that recording can be made. Based on this copyright information signal Scr, the recording control unit 111 outputs a recording control signal Sc for allowing the recording processing operation. Based on the recording control signal Sc, there cording processing unit 106 performs the recording processing operation or continues the timer-controlled recording operation.
FIG. 16 schematically illustrates recording areas of the recording medium of the recording unit 107. The recording medium of the recording unit 107 is broadly divided into three areas: a filing system information area AFS, a video file management information area AAD, and a video file area AAV, which are listed in increasing order of physical address. The video file area AAV stores video files which are output as the MPEG image signals Smpg from the recording processing unit 106 of the video signal recording apparatus DRc1 so as to be recorded on the recording unit 107. The filing system information area AFS records filing system information indicating which video files are recorded in which address of the video file area AAV.
The video file management information area AAD records video file management information including a recording start time, a recording time length, a recoding TV channel, a recoding TV program, and recoding mode information. The video file management information can specify the contents of each video file recorded in the video file area AAV. With the use of the video file management information, it is possible to present the contents of the recoded video file to the user. The video file management information is fed to the video signal recording apparatus DRc1 through a means (not shown) for detecting the state of user's operation and the channel of the analog video signal Sva input to an input terminal 20.
The number of files that can be managed in each of the filing system information area AFS and the video file management information area AAD is not uniquely related to the recording capacity of the video file area AAV. Therefore, however spaces remain in the hard disk, they cannot be used when the number of managed files passes the upper limit.
The capacity of each of the filing system information area AFS and the video file management information area AAD is set to be significantly smaller than that of the video file area AAV. Once the filing system information area AFS is completely consumed, the recording unit 107 cannot record video files anymore even if unused recording areas remain in the video file area AAV. Furthermore, once the video file management information area is completely consumed, the contents of the video files recorded on the video file area AAV cannot be specified anymore.
With reference to FIG. 17, a video signal recording apparatus disclosed in Japanese Patent Laid-Open Publication No. 2001-14793 is described below, in which a pre-process for replay is omitted for a copying-prohibited input signal. A video signal recording apparatus DRc2 includes a recording medium drive control unit 50, a recording medium 51, a signal recording/replaying processing unit 52, a deshuffling processing unit 53, a deshuffling control unit 54, a copyright information detecting unit 55, a video signal processing unit 56, an external signal input unit 57, a video signal output unit 58, and a monitor 59. The recording medium 51 is preferably a medium having digital signals recordable thereon and reproduced therefrom, and is typically a magnetic tape, an optical disk, or a magnetic disk.
The recording medium drive control unit 50 drives the recording medium 51 to perform an operation of recording video/audio signals. The external signal input unit 57 receives an external input signal to be recorded on the recording medium 51 for supply to the video signal recording apparatus DRc2. The video signal processing unit 56 performs, in response to a recording/replaying operation, video signal processing, such as compression, decompression, error correction, and shuffling. The video signal output unit 58 outputs the replayed recorded video to the monitor 59. The signal recording/replaying processing unit 52 replays the video signal recorded on the recording medium 51, and records the video signal on the recoding medium 51.
At the time of replaying, the deshuffling processing unit 53 deshuffles video signals supplied by the signal recording/replaying processing unit 52, and then outputs the resultant signals to the video signal processing unit 56. At the time of recording, the deshuffling processing unit 53 deshuffles signals supplied by the video signal processing unit 56, and then outputs the resultant signals to the signal recording/replaying processing unit 52.
The deshuffling control unit 54 controls the deshuffling operation of the deshuffling processing unit 53 to start or stop at the time of recording/replaying, and also controls the driving operation of the recording medium drive control unit 50. The copyright information detecting unit 55 detects various information including copyright information contained in the external input signal at the time of recording.
The recording operation of the above-structured video signal recording apparatus DRc2 is described below. First, an external video signal Sve to be recorded on the recording medium 51 is fed through the external signal input unit 57. The external video signal Sve is typically a tuner input video signal of analog broadcasting or a video signal input through an analog external input terminal.
Next, the external video signal input through the external signal input unit 57 is supplied to the video signal processing unit 56 for video signal processing. When the external video signal Sve is an analog signal (Sva), the external video signal Sve is output through the video signal output unit 58 to the monitor 59 for presenting video to be recorded on the recording medium 51. Furthermore, the video signal processing unit 56 extracts copyright information from the input external video signal Sve (Sva), and also performs a band compressing process to convert the external video signal Sve (Sva) to a digital signal (Svd).
Next, the extraction result obtained by the video signal processing unit 56 is identified by the copyright information detecting unit 55. As a result of the identifying process, if the external video signal Sve is “recordable”, that is, copying is permitted, or if no copyright information or no copyguard signal is provided to the external video signal Sve, the deshuffling control unit 54 is controlled so that the deshuffling processing unit 53 performs a deshuffling process. If the external video signal Sve is “not recordable”, that is, copying is prohibited, the deshuffling control unit 54 is controlled so that the deshuffling processing unit 53 does not perform a deshuffling process. Then, the video signal output from the deshuffling processing unit 53 is recorded by the signal recording/replaying processing unit 52 on the recording medium 51.
Another recording apparatus is disclosed in Japanese Patent Laid-Open Publication No. 9-180295 (1997-180295), in which a signal to be recoded is muted while copying is prohibited and, once prohibition is removed, a recording operation is started. In this recording apparatus, copying-prohibition data included in the signal to be recorded is detected in order to control the recording operation of the recording system. The recording operation is in a wait state for portions of which recording is prohibited until copying prohibition is removed, and is performed for portions other than the above copying-prohibited portions. While a copying detection signal is being detected, the signal to be recorded is muted, but recording itself is not interrupted, thereby allowing the entire program of television broadcasting to be recorded, for example. Note that, in this recording apparatus, received signals of analog television broadcasting, received data of digital television broadcasting, and digital signals supplied from a computer through an I/O interface to the recording system can be also supplied to the recording system after being muted by a relevant muting circuit.
The above-described video signal recording apparatus which stops recording for each copyrighted work requires a complicated process of notifying the user that recording is stopped. For example, consider a case where a user starts manual recording by pressing a recording start button, and external video signals are copyrighted and are therefore copying-prohibited. In this case, some measures have to be taken so as to stop or not to start the recording operation, and also so as to display a message indicating, for example, that “recoding is prohibited by copyright” on a monitor screen.
Moreover, timer-controlled recording, which automatically starts recording by a timer, requires a process more complicated than that of manual recording. That is, if recording of the program set by timer-controlled recording is prohibited by copyright, the information about prohibition has to be held until the user next operates the recording apparatus. Then, for example, when the user next operates the recording apparatus, a message indicating that recording is prohibited is displayed on the screen of the monitor. This requires very complicated processes, making it difficult to develop software for the recording apparatus.
Still further, consider a case where the input terminal of the recording apparatus is connected to an analog output of a tuner for digital satellite broadcasting. In digital satellite broadcasting, rain could degrade the reception state, causing a weak electric field. In such a weak electric field, copyright information (copyguard signal) included in digital satellite broadcasting may not be able to be correctly detected by the tuner. For example, the copyright protection information of the input video signal is detected as being frequently changed. In one case, a CGMS-A signal of a program is detected as being alternately indicative of “copying-prohibited” and “copying-permitted”.
As described above, in the case where the video signal whose copyright protection information is frequently changed is supplied in a weak electric field caused by rain, for example, the video signal recording apparatus DRc1 starts and stops recording alternately and repeatedly. In recording apparatuses using a hard disk, data from starting recording to data at the stopping of recording are managed as a single video file. Also, each video file includes management information for the purpose of later displaying the recorded video files as a list. Therefore, repetition of starting and stopping recording creates a large number of video files, consuming a large amount of the filing system information area AFS and the video file management information area AAD. This makes it impossible to efficiently use the filing system information area AFS. At the worst, some video files cannot be recorded.
In the filing system, the limitation on the number of manageable files and the capacity of the hard disk have a tradeoff relationship. Therefore, the limitation on the number of manageable files can be mitigated by increasing the capacity of the hard disk, as well as the power of the CPU for managing a large number of files. In commercial recording apparatuses, however, it is a waste to use a CPU of overly high capability to perform only file management processing only for the purpose of managing a large number of files. This is one reason for limiting the number of files.
Moreover, if the capacity of the hard disk is increased without extending the filing system, the areas of the hard disk are not efficiently used. Extension of the filing system may alleviate inefficient use of the hard disk, but may require more capability of file management.
In the above-described video signal recording apparatus (Japanese Patent Laid-Open Publication No. 2001-14793), copying-prohibited external video signals are recorded on the recording medium without being deshuffled. In this case, the original external video signals without being deshuffled are recorded on the recording medium, meaning that the original external video signals can be extracted as they are. This does not provide complete protection of copyright of the original external video signals.
Moreover, upon stopping a deshuffling process, the above-described video recording apparatus is not capable of notifying the user that the deshuffling process has stopped for copyright protection. For example, if video signals indicative of a white or black full-screen picture are supplied, video signals to be recorded with deshuffling and those to be recorded without deshuffling provide exactly the same image. Therefore, the user cannot know from the replayed video whether the video is copyright-protected.
Furthermore, in the above-described recording apparatus (Japanese Patent Laid-Open Publication No. 9-180295), the user cannot ascertain which reason correctly explains why a portion has been muted at the time of replaying, due to a lack of an input signal or copyright protection. In order to allow the user to ascertain the reason of the mute, a complicated process is required for notifying the user that the mute has been performed for the purpose of copyright protection.
Still further, in order to record signals containing information representing a copyrighted work, such information is replaced by information representing a non-copyrighted work. From the recorded information representing the non-copyrighted work as a replacement, the information representing the original copyrighted work cannot be recovered. That is, the original work has been discarded. Therefore, when permission for using the original work is obtained later, the original work has to be again obtained (received and recorded).